Hydrolock Prevention

On two occasions while on a mooring the seas kicked up and were hitting on the starboard aft quarter and hydrolocked my engine. Our 350 is a 2002 model with a single Yanmar 6LYASTP.


The first time was nearly catastrophic, with sea water in the cylinders, crankcase and intake manifold. Quick action after being towed 25 miles to my slip removed the water and saved an overhaul, but I'm still seeing traces of sodium in the oil analysis.


The second time happened when I was ashore and didn't think it was that rough. I returned to the boat and caught it before more than a cylinder of two flooded. Just had to pull the injectors.


This also happened to a friend with a Ranger Tug with this engine.


I now pop a 2.5qt plastic paint bucket in the exhaust outlet when not in a totally protected area.


I'd like a more permanent solution that doesn't include require spending a couple of boat units and redesigning the exhaust to add more rise.


Am I the only Mainshpper who's had this happen?


Prevention suggestions? I've considered adding a flap, but undeway the exhaust outlet orientation might make a flap problematic.

I have two inflatable green rubber balls with a place to attach a line I got at West Marine that fit into our exhaust outlets. Our owner's manual (Bertram) specifically says to take care to avoid water intrusion in the exhausts when anchored, with a danger of a following sea. They fit inside perfectly, are easy to pull out, and would probably blow out if I ever cranked the engines without remembering to remove them.

Here are some things that have been tried (and some worked):

A flapper on the exhaust exit at the transom. Centek makes them. Probably the cheapest and easiest thing you can do.

A surge tube in the exhaust. This tube absorbs surges and doesn't let the water get up into the turbo or exhaust manifold.

A redesigned exhaust system that adds to the height above water. Expensive, yes. I did this on my Pilot 34 and it cost me less than a grand for parts and welding. I designed and installed it myself.

David

My old boat had a seacock on the generator's exhaust. That was nice.

On my new boat, I don't have that. But, when I bought the boat, the person who did some initial work recommended moving the muffler and exhaust far forward, actually forward of the genset, in order that the exhaust pipe could be raised higher above the water line before it drops in.

It cost a good b it because the exhaust hose ain't cheap. And, it was less convenient having it come forward into a busy part of the engine room. But, it did raise it about a foot, which I imagine is good.

Does your exhaust have a large up loop?

There should be enough room on a 350/390 to raise the elbow above the waterline enough to prevent hydrolock.
A surge tube will also help prevent it.

Another suggestion would be to give a call to Seaboard Marine in Oxnard and talk with Tony Athens. He is familiar with this problem on that style Mainship.
He'll have a solution that will work.

If I'm not mistaken you have a lift muffler, and on 390 models I have seen there is an "overflow port" near the top of the muffler for when water reaches that high it is directed through this port to overboard. This is specifically for hydrolock protection.
If you have this set up is the drain open to overboard? The "overflow port" is near the top of the muffler on the side and well below the exhaust elbow and should protect from hydrolock
I believe they also did something similar on the Polit 34's

Sounds like you have dodged a bullet twice and I'll bet your insurance company would expect you to take action.
As a temp. measure the balls with strings seem like a good idea.
The external flaps I see alot but anchored in a seaway, when the transom plunges the flap opens so N/G
The Centec internal check valves are another option that don't suffer from that shortcoming but I would not trust them as a complete solution either.
Installing a properly designed system is the only complete answer. This could even involve waterlift mufflers and goosenecks at the transom b/4 you could safely anchor in the tradewinds. Without goosenecks, water will roll up the exhaust as you "hobbyhorse" at anchor, the waterlifts will fill and then fill the engine.

While I didn't have this happen, I was worried it could. Sole of my main deck is about 12-inches above waterline and getting the exhaust high enough was impossible without heroic measures.

I pinged this forum a couple times, and also pinged "Ask Steve [d'Antonio]". I didn't get an absolute "here's the right answer" response, but best I could figure, best solution for me was a gooseneck before exhaust exits the hull. Now, my boat (like Brooksie
s) has a raised bench at the fantail so there's room to raise the exhaust.

https://www.vetus.com/en/exhaust-systems/gooseneck.html

But as Brooksie states, you have dodged a bullet. You have a relatively common boat so I'd wager something has been changed or there's be a ton of MS 390's with blown engines.

Peter

Peter. I'm assuming then that Weebles already had a waterlift behind the engine allowing you to add a gooseneck? Seeker did not so one needed to be added. I made my gooseneck from hose and f/g elbows wasn't crazy about the plastic goosenecks.

This just sounds like poor exhaust design and engine installation. Get that exhaust raised and redesigned.

Arc said:

This just sounds like poor exhaust design and engine installation. Get that exhaust raised and redesigned.

Click to expand...

An exhaust redesign is a great idea, but A LOT more expensive than a 2 1/2 quart paint bucket!

Brooksie said:

Peter. I'm assuming then that Weebles already had a waterlift behind the engine allowing you to add a gooseneck? Seeker did not so one needed to be added. I made my gooseneck from hose and f/g elbows wasn't crazy about the plastic goosenecks.

Click to expand...

Brooksie said:

Peter. I'm assuming then that Weebles already had a waterlift behind the engine allowing you to add a gooseneck? Seeker did not so one needed to be added. I made my gooseneck from hose and f/g elbows wasn't crazy about the plastic goosenecks.

Click to expand...

I struggled with my exhaust system. When I got the boat it had just a plain water injector elbow off the engine exhaust manifold. 45 degree bend down, no loop, to a lift muffler. Then up along the sole to the back where it raised up and exited the hull higher than the sole - exit was the highest point of the exhaust system.

Several years ago I added an exhaust elbow that looped as high as possible, but the exhaust outlet through the hull was still the high point (I also added a rubber flap on the exhaust pipe).

I talked to a lot of people and never really came up with a good design that I liked a lot, just less bad than others. The plastic gooseneck is that "least bad" solution.

I forget if it was you or Island Cessna that put a loop above the cabin sole. This is a very sound design, the best from an exhaust design perspective. But would seriously interrupt my interior layout. And I had to ask myself "it's worked for 50 years...."

The biggest problem with small cruising boats is simply finding the space for stuff. The W36 is plenty big for moving along oceans, but space fills up quickly. Fuel tanks line the outboard sides of the engine room, water tanks behind. No way to run the exhaust out the side, probably the other best solution.

One of the few items I feel like I resolved, but never solved.

Peter

jbbmillar said:

An exhaust redesign is a great idea, but A LOT more expensive than a 2 1/2 quart paint bucket!

Click to expand...

...... But not nearly as expensive as a failed exhaust system.

Seriously, you dodged a couple bullets. "you gotta ask yourself.......do you feel lucky today? Do ya?"

DavidM said:

A redesigned exhaust system that adds to the height above water. Expensive, yes. I did this on my Pilot 34 and it cost me less than a grand for parts and welding. I designed and installed it myself. David

Click to expand...

David
Aren't some Mainship install and designs problematic in this regard and require a re-design as you mention?

Water getting into an engine from the exhaust side is the cause of many engine issues and failures. The OP may want to visit boatdiesel and sbar websites for information on this all too common type of problem. It may be worthwhile to pull the turbo and have a good look to assess any damage to-date

Following.

Our new-to-us generator is being rebuilt and I believe a similar phenomena was the problem. We were considering a pvc test plug sized to the exhaust for when it's not in use

Hard to recommend a solution without knowing the levels and space available in a boat.

I'm lucky enough to have plenty of vertical space at the stern (up to the top of the wide gunwales) allowing a high loop with the exhaust hose before exiting.

sunchaser said:

David
Aren't some Mainship install and designs problematic in this regard and require a re-design as you mention?

Click to expand...

Yes the 390s were very problematic. I know of several owners who hydrolocked their CATs and two who lost the engines and one who was lucky and only lost a turbocharger. They were all 3126 engines.
Seems the 3116s were fine.

Yanmar makes a dry 90deg dry cast iron elbow that can be added between the turbo outlet and mixer inlet. With a little finagling, you can get some more height for not too much money.

I had a new custom mixer made for the purpose of PM . I could not afford a complete failure of a $50k engine, when it could be prevented.

jbbmillar said:

On two occasions while on a mooring the seas kicked up and were hitting on the starboard aft quarter and hydrolocked my engine. Our 350 is a 2002 model with a single Yanmar 6LYASTP.


The first time was nearly catastrophic, with sea water in the cylinders, crankcase and intake manifold. Quick action after being towed 25 miles to my slip removed the water and saved an overhaul, but I'm still seeing traces of sodium in the oil analysis.


The second time happened when I was ashore and didn't think it was that rough. I returned to the boat and caught it before more than a cylinder of two flooded. Just had to pull the injectors.


This also happened to a friend with a Ranger Tug with this engine.


I now pop a 2.5qt plastic paint bucket in the exhaust outlet when not in a totally protected area.


I'd like a more permanent solution that doesn't include require spending a couple of boat units and redesigning the exhaust to add more rise.


Am I the only Mainshpper who's had this happen?


Prevention suggestions? I've considered adding a flap, but undeway the exhaust outlet orientation might make a flap problematic.

Click to expand...

I don't understand if on aa mooring bow to - how water could come back up the exhaust and flood the motor, I would think you would have to moored stern to?

Cartouche said:

I don't understand if on aa mooring bow to - how water could come back up the exhaust and flood the motor, I would think you would have to moored stern to?

Click to expand...

Because your almost level exhaust piping is hobbyhorsing up and down and rolls the seawater right up and over the little 7-8" hump at the turbo.
Even with a waterlift muffler, it must fill the muffler first, but the same thing happens. The gooseneck aft keeps the water out and the waterlift allows you to have a gooseneck.

Brooksie said:

Because your almost level exhaust piping is hobbyhorsing up and down and rolls the seawater right up and over the little 7-8" hump at the turbo.
Even with a waterlift muffler, it must fill the muffler first, but the same thing happens. The gooseneck aft keeps the water out and the waterlift allows you to have a gooseneck.

Click to expand...

Appreciate the explanation although I know I would not enjoy anchoring if the sea state was that violent as you can see by the attached picture on our Mainship 390 - the U in the exhaust is Higher than the engine almost level with the floor, that is a heck of a rise. Glad to know the limitations

Anchoring in a seaway is not a choice usually but something that happens more or less often depending on where you are and weather conditions there.

But if you have been hydrolocked at your home mooring, you have a problem.
The deciding factor is not the relationship between your spillover point and your cabin sole rather between the spillover point and the waterline which in your case is too close.
Don't take our word for it, easy to educate yourself online.

Arc's post above shows a classically bad exhaust installation from the maker and a proper solution in the lower picture. It may not fix the OP's problem but others should examine their exhaust for similar bad installations

bayview said:

Arc's post above shows a classically bad exhaust installation from the maker and a proper solution in the lower picture. It may not fix the OP's problem but others should examine their exhaust for similar bad installations

Click to expand...

Yes and no. Yes, the lower picture shows a riser which is not completely water jacketed so is unlikely to leak into the engine when it fails. No, without knowing spillover height above waterline, both look the same and could be as bad as jbbmillar's situation.

Brooksie said:

Yes and no. Yes, the lower picture shows a riser which is not completely water jacketed so is unlikely to leak into the engine when it fails. No, without knowing spillover height above waterline, both look the same and could be as bad as jbbmillar's situation.

Click to expand...

Brooksie
Yes, the overall geometry to the waterline is important as well as the entire exhaust run layout. But Bayview's point is correct with the bottom photo in Arc's post #20 case being much superior to the upper picture. Arc seems a bright fellow and I'd wager he has the geometry properly figured out.

I was referring to the prevention of hydro lock or water intrusion by internal failure of the water jacket.

bayview said:

I was referring to the prevention of hydro lock or water intrusion by internal failure of the water jacket.

Click to expand...

That's what I thought, failure of jacketed riser. Because the two pictures, other than the jacketing vs:lagging, show the same thing and say nothing of the waterline to spillover height relationship.


"In order to fix a problem, first you have to admit you have one."

Years ago, I broke the crankshaft of a single cylinder Volvo diesel in a small sailboat(a 26ft Folkboat). It had a Vetus 'gooseneck" trap and a high hose loop, but on stbd tack, well heeled for a couple of hours, water went up the above normal waterline stbd exhaust outlet, despite the protections, all the way to the engine. A flap at the exhaust exit sounds a good idea. We replaced the engine.